1. Field of the Invention
The present invention relates to a novel silver halide color photographic light-sensitive material for recording images and to a method for forming color images using the material.
2. Description of the Related Art
Owing to the remarkable development of color photographic light-sensitive materials utilizing silver halides in recent years, high-quality color images are now easily available. For example, according to so-called ordinary color photography, color prints are obtained by taking a photograph utilizing a color negative film, processing the film, and optically printing the image information which is recorded in the processed color negative film onto color photographic printing paper. Recently, this process has made remarkable progress, and large-scale, centralized color laboratories, in which a large quantity of color prints are produced efficiently, and the so-called mini-labs which are installed in shops and are designed to use compact and simple printer-processors have spread widely. Therefore, anybody can enjoy color photography easily.
In addition, recently, a new concept, the APS system, which utilizes a color negative film capable of recording as a magnetic record a variety of information by using a support coated with a magnetic material, is being put on the market. Using this system photography is made even more enjoyable by allowing the size of the prints to be changed using information recorded at the time the photograph was taken, and by the general simplicity with which the film can be handled. Also proposed is a tool which edits or processes images by reading the image information from processed negative film by means of a simple scanner. Since these means make it possible to easily digitize high-quality image information from silver salt photographs, the enjoyment taken in conventional photography is in the process of being surpassed by a wide range of easily accessible applications.
The color photography, now in common currency, use the optical printing system using color reproduction by the subtractive color process. Generally, a color negative film comprises a transparent support and light-sensitive layers thereon utilizing silver halide emulsions as light-sensitive elements sensitive to blue, green or red wavelength regions respectively, and so-called color couplers capable of producing a yellow, magenta or cyan dye having a complementary hue of the sensitive wavelength region of each light-sensitive layer. A color negative film exposed during photography, is processed in a color developing solution containing an aromatic primary amine developing agent. At this time, the developing agent develops, i.e., reduces the exposed silver halide grains, and the oxidized form of the developing agent, which is formed concurrently with the foregoing reduction, undergoes a coupling reaction with the color coupler to form dyes. The metal silvers (developed silver) generated by the development and the unreacted silver halides are removed through a bleaching and fixing process, respectively. This creates a color image on the color negative film. Subsequently, color photographic printing paper, which comprises a reflective support and light-sensitive layers coated thereon having a combination of light-sensitive wavelength regions and hue in each layer, similar to the color negative film, is optically exposed to light through the processed color negative film, and is then subjected to the color developing, bleaching and fixing processes as in the case of the negative film to obtain a color print having a color image composed of dye images so that an original image can be reproduced. In contrast with the above-described classic methods for forming images, recently it has become possible to enhance the image quality of print by converting the image information recorded on a color negative into digital information by means of a scanner and processing the digitized information in various ways. Mini-lab systems which perform the above-described process have actually been announced.
Because of this background, there is a growing demand for the simplification of the image forming method of the color negative. The first reason for this is that expertise and skilled operation are necessary due to the requirement of strict control of the composition and the temperature of the solutions in processing baths for the above-mentioned procedure consisting of color development, bleaching and fixation. The second reason for this is that equipment to be used exclusively for the developing process is often required, due to substances, such as developing agents and bleaching agents comprising an iron chelate compound, the discharge of which is regulated from the standpoint of environmental protection. The third reason for this is that the currently available systems do not satisfactorily fulfill the requirement for rapid reproduction of recorded images. The above-mentioned processes still take time, although this time has been shortened with recent advances in technology. From this background the demand is increasing for reducing the burden on the environment by creating a system which doesn't utilize bleaching agents or color developing agents as used in current image forming systems and for thereby further improving the ease of use. In order to compete with electronic still photography and similar systems it is imperative to continue improving the ease of use of image forming methods which use processing solutions.
From these standpoints, many improved technologies have been proposed. For example, IS & T's 48th Annual Conference Proceedings, p. 180, discloses a system in which the dye formed in the developing reaction is transferred to a mordant layer and thereafter a light-sensitive material is stripped to remove the developed silver and unreacted silver halide from an image formed by the dye without the use of a bleach-fixing bath which has been indispensable to conventional color photographic processing. However, this technique cannot perfectly solve environmental problems because a developing process using a processing bath containing a developing agent is still necessary.
Fuji Photo Film Co., Ltd. has proposed Pictrography system which dispense with a processing solution containing a developing agent. In these systems, a small amount of water is supplied to a light-sensitive member containing a base precursor, and then the light-sensitive member and an image receiving member are placed face to face and heated to promote the developing reaction. This system does not use the aforementioned processing bath and, in this regard, is advantageous with respect to environmental protection. Accordingly, it is clearly conceivable that this system can be utilized for image formation in light-sensitive materials for photographic.
For example, Japanese Patent Application Laid-Open (JP-A) No. 9-10,506 and European Patent No. 762,201 describe a method whereby a color image is obtained in a light-sensitive material by a developing agent and a coupler contained in the light-sensitive material.
This Pictrography system can dispense with a developing solution, and the processing can be carried out by merely supplying a small amount of water. According to this system, the generation of a base, which is necessary for the progress of heat development, is realized by the above-described simple method. Therefore, developed silver and undeveloped silver halide remain in the light-sensitive material after the heat development. If this system is applied to a light sensitive material for photography, then, as it is necessary to obtain an extremely sharp image, various problems arise due to the necessity of using an image formed on a light sensitive material.
As is generally known, since silver halide grains have a larger refractive index compared with a binder such as gelatin, and since a silver iodobromide emulsion, which can provide high sensitivity for photography, has absorption in a blue color region, so the remaining silver halide causes significant light scattering and thus hinders the reading of the formed image. Therefore, whether to establish a method in which the silver halide grains, which are a light scattering substance, can be removed with the same simplicity as in Pictrographic heat development, or to establish a method in which the image information can be read from a light-sensitive material containing the light scattering substance at a high density, is an important subject.
From the above point of view, silver chloride has an advantageous physical properties as a silver halide in comparison with the silver iodobromide generally utilized in photographic light-sensitive materials, because the refractive index of silver chloride is small and silver chloride has little light scattering due to it having no absorption in the visible light region. In addition to the above properties, silver chloride is preferable due to its rapid fixing speed allowing the silver halide to be removed easily.
Several attempts are known to impart the required high sensitivity to photographic light-sensitive materials by using silver chloride. Although the most effective way of imparting high sensitivity is to increase the amount of light absorbed by each single silver halide grain, merely increasing the grain size is accompanied by such undesirable results as poor graininess and a decrease in the developing speed. Therefore, designing the silver halide grains with a tabular form has the advantage of increasing the area of each grain which can receive light. Examples of these attempts are described in, e.g., U.S. Pat. Nos. 4,399,215, 4,400,463 and 5,217,858, wherein the photographic emulsions comprise tabular high silver chloride grains which are each made up of a (111) plane as a principal face.
Meanwhile, U.S. Pat. Nos. 5,292,632 and 5,310,635 disclose a photographic emulsion composed of tabular high silver chloride grains which are each made up of a (100) plane as a principal face. Although silver chloride grains are known to tend to form a (100) plane as a prevailing face when growing into fine crystals, a strict control of reaction conditions is necessary for preparing tabular grains having the desired shapes and sizes while holding a (100) plane as the principal face, and therefore a simple manufacturing process is difficult to establish.
In the preparation of a practical photographic material, plural kinds of emulsions having different levels of sensitivity need to be used in order to obtain a broad latitude. When viewed from this standpoint, the use of tabular grains having a (111) plane as a principal face is desirable, because the manufacturing process of these grains is more likely to be simplified.
Based on these technologies, an attempt was made to produce tabular grains having a high silver chloride content and being made up of a (111) plane as a principal face and also being characterized by little light scattering and ease in fixing. These grains-were used for the preparation of a photographic light-sensitive material which would enable a simple heat development in the aforementioned Pictrography system. However, this attempt faced serious problems.
In a simple heat developing system suited for the purpose of the present invention, such as the Pictrography system, it is difficult to obtain the high level sensitivity required for photographic light-sensitive materials by using an emulsion having a high silver chloride content. But employment of a higher level of chemical sensitization, for obtaining a higher level of sensitivity, tends to cause serious fogging, and the creation of good discrimination is difficult. Further, it has been found that, when an emulsion having a high silver chloride content is used, the sensitivity of a light-sensitive material prepared by using a coating liquid after the passage of time tends to decrease, and the sensitivity of the light-sensitive material stored for a long time tends to decrease